The CV4005 is a special quality version of the commercial U78 miniature HT full wave rectifier. The construction is of two anodes set around a common cathode assembly.Comparing the images of the U78 and the CV4005 it can be seen that the the SQ version has double micas top and bottom.
Research into modes of failure of valves subject to vibration, as found in aircraft etc., found that adding a second sheet greatly reduced the destruction of the mica.
The the two identical anodes are mounted one up and one down around the central cathode.
The GEC logo. The anodes are mounted at 90 degrees to one another. Here one is facing the camera and the other is face on.
The thin glass tube envelope is 18 mm in diameter and, excluding the B7G base pins, is 60 mm tall.
References: Data-sheet & 1040. Type CV4005 was first introduced in 1959.